Concentric growths on Hornbeam bark

Concentric growths on Hornbeam bark

Observation - Concentric growths on Hornbeam bark. Description: Large concentric rings of hard woody tissue in several places on this hornbeam coppice. Very grateful for any clues as to what causes this and whether we should be concerned.

Large concentric rings of hard woody tissue in several places on this hornbeam coppice. Very grateful for any clues as to what causes this and whether we should be concerned.